A US Air Force base in Colorado has admitted to accidentally releasing 150,000 gallons of water containing toxic chemicals into the sewer system of nearby Colorado Springs.

Peterson Air Force base said on October 18 that the water contained perfluorinated compounds (PFCs), chemicals used on bases to put out fires and which have been linked to several kinds of cancer, low birthweight in babies and other health issues. The Air Force statement has not clarified how high the levels were.

Officials from nearby communities and the Colorado Department of Public Health have assured residents that the contaminated water has not reached drinking water sources, only sewers.

The wastewater first passed through a treatment plant, but the plant is not designed to remove PFCs. The wastewater then flowed into Fountain Creek. Fountain Creek flows south toward Pueblo and into the Arkansas River, the Denver Post detailed.

The spill was discovered October 12, according to an Air Force statement, but could only be pinned down as having happened at some point during the previous week. The base said they were investigating the incident and reviewing training and operating procedures.

CBS news reports that the process of releasing wastewater is not a simple one. "There is at least two valves that have to be turned on, and the electrical control for this is above ground," base environmental chief Fred Brooks explained in their report. "That's separate from that, so it's at least a three-step process."

"Peterson Air Force Base and the US Air Force are committed to protecting the environment and communities in which we call home," said Colonel Doug Schiess, 21st Space Wing commander, in the base statement. "We take all environmental concerns seriously, and have opened an investigation to determine the cause of the discharge and to prevent it from happening again."

Pueblo Board of Water Works spokesman Paul Fanning said his community did not hear about the spill until reporters began making inquiries October 17, the Denver Post reported.

"We don't use any groundwater or surface water from Fountain Creek. We use water from the Arkansas River taken upstream from where Fountain Creek flows in," Fanning said. "But it is not a good thing to have those contaminants anywhere in our water. There are some reported health effects. It is in our interest to protect our public."

Last year, PFCs were discovered in public water sources in the vicinity of Colorado Springs near Fountain Creek and Windmill Gulch.

According to the Peterson Air Force Base statement, "When PFCs were discovered earlier this year in well water south of the base, the Air Force proactively provided $4.3 million to filter and provide drinking water to affected residents while an investigation of potential source areas is conducted. Officials are confident these ongoing mitigation strategies are sufficient to address any potential contamination from the discharge."

In the past few years, groundwater around bases in California, Texas, Michigan and Pennsylvania has been found to be contaminated with carcinogens, including PFCs.